UCLA Clinical Microbiology, University of California, Los Angeles, California, USA.
Deaconess Health System, Evansville, Indiana, USA.
J Clin Microbiol. 2018 Feb 22;56(3). doi: 10.1128/JCM.01678-17. Print 2018 Mar.
The performance of a disk diffusion test using broth from positive blood cultures as inoculum (direct disk diffusion [dDD]) was evaluated for a collection of 20 challenge isolates of , , and Isolates seeded into human blood were inoculated into Bactec Plus Aerobic/F, VersaTREK Redox 1, and BacT/Alert FA Plus bottles and incubated in the respective automated blood culture systems. Disk diffusion results were compared to reference disk diffusion results. Categorical agreement (CA) values for dDD, after removal of random errors due to natural MIC variation, were 87.8%, 88.4%, and 92.2% for the BacT/Alert, Bactec, and VersaTREK systems, respectively. No very major errors (VME) were observed, and major error (ME) rates were 3.0%, 2.3%, and 1.7%, respectively. Incubation of the dDD test samples for 6 h compared to incubation for 16 to 18 h resulted in 19.9% of tests having too light of growth to allow reading of zones of inhibition. Among the evaluable dDD tests, CA values were 58.9%, 76.6%, and 73.2% for the isolates seeded into the BacT/Alert, Bactec, and VersaTREK systems, respectively. VME rates for isolates seeded into these systems were 2.2%, 1.8%, and 3.0%, respectively, and ME rates were 25.4%, 6.1%, and 2.8%, respectively, at the 6-h reading. The best performance of dDD was found for blood cultures with bacterial concentrations in the range of 7.6 × 10 to 5.0 × 10 CFU/ml; CA values ranged from 94.7 to 96.2% for these concentrations after 18 h of incubation and from 76.9 to 84.1% after 6 h of incubation. These preliminary data demonstrate the potential accuracy of dDD testing by the clinical laboratory.
使用阳性血培养物作为接种物的纸片扩散试验(直接纸片扩散 [dDD])性能,对 20 株 、 、 和 的挑战分离株进行了评估。将接种入人体血液的分离株接种到 Bactec Plus Aerobic/F、VersaTREK Redox 1 和 BacT/Alert FA Plus 瓶中,并在各自的自动化血培养系统中孵育。将纸片扩散结果与参考纸片扩散结果进行比较。经过去除由于自然 MIC 变化引起的随机误差后,dDD 的分类一致性 (CA) 值分别为 BacT/Alert、Bactec 和 VersaTREK 系统的 87.8%、88.4%和 92.2%。未观察到非常大错误 (VME),主要错误 (ME) 率分别为 3.0%、2.3%和 1.7%。与孵育 16 至 18 小时相比,将 dDD 测试样本孵育 6 小时会导致 19.9%的测试样本生长过轻,无法读取抑菌环的大小。在可评估的 dDD 测试中,接种到 BacT/Alert、Bactec 和 VersaTREK 系统中的分离株的 CA 值分别为 58.9%、76.6%和 73.2%。接种到这些系统中的分离株的 VME 率分别为 2.2%、1.8%和 3.0%,ME 率分别为 25.4%、6.1%和 2.8%,在 6 小时读数时。在细菌浓度范围为 7.6×10 至 5.0×10 CFU/ml 的血培养中,dDD 的性能最佳;孵育 18 小时后,CA 值范围为 94.7%至 96.2%,孵育 6 小时后,CA 值范围为 76.9%至 84.1%。这些初步数据表明临床实验室进行 dDD 测试具有潜在的准确性。